9v to 5v for arduino pro mini

You have the 9V connected to the RAW pin?
The sensors/motors run from the 9V?

A Motor using those small 9 volt batteries are almost always a losing situation.

Lefty

there is a tilt sensor attached directly to the 9v pin, the power shouldn't damage the sensor, im just worried that the power going into the arduino through the digital pin from the sensor is damaging the arduino, i need to know which value of resistor to put between the battery and the raw pin to avoid damage to the arduino and the servo, thanks very much :slight_smile:

i need to know which value of resistor to put between the battery and the raw pin to avoid damage to the arduino and the servo, thanks very much

Wrong solution for the wrong problem. Powering a servo from the pro mini's +5vdc power is what will overheat the regulator. That's if the little 9 volt battery can even supply enough current to overheat anything.

I think you need to reevaluate all your loads for what current they draw, what voltage they require, how long the project must run between battery replacements. Only then can you see what size battery your project will require. Those little 9 volt batteries don't work with servos worth a darn......

Lefty

it is a very small servo, i prototyped it on a freeduino and a breadboard and the 5v from the arduino was enough, it only needs to move 180 degrees to release the parachute so it isnt going to drain the battery quickly,

sholtob:
it is a very small servo, i prototyped it on a freeduino and a breadboard and the 5v from the arduino was enough, it only needs to move 180 degrees to release the parachute so it isnt going to drain the battery quickly,

OK, so what is the problem you are having, not the solution you think you need to apply (adding a series resistance to the battery is almost never a solution worth pursuing).

Lefty

the problem is the arduino chip is heating up

Well the pro mini is designed to handle 9vdc input to it's raw pin and uses it's on-board voltage regulator to create the +5vdc needed by the AVR chip.

Maybe if you could draw up how you are wiring everything up (battery, pro-mini, servos, sensor), we can see what's what. What specifically is getting hot, the 328p chip? the voltage regulator chip?

Lefty

as i said, the problem is the power going through the tilt switch into digital pin 2, so if you know the value of resistor that would be best for turning 9v into 5v so that it is the same as the output on a normal arduino board?

sholtob:
as i said, the problem is the power going through the tilt switch into digital pin 2, so if you know the value of resistor that would be best for turning 9v into 5v so that it is the same as the output on a normal arduino board?

Could you provide the datasheet for the tilt switch? If it's a simple switch contact why don't you just wire it to +5vdc rather then +9vdc?

Lefty

Have you mentioned a tilt switch before?
Why don't you tell us what you've got and what you want to do?

i mentioned the tilt switch in my first post, i had no idea there was a 5vdc output on the pro mini, can you describe where it is?, thanks very much for all the help by the way :slight_smile:

I'm afraid you're going to have to point me to the tilt switch reference in the first post.

Punctuation would be useful too.

there is a tilt sensor attached directly to the 9v pin

it was actually in my second post but i did mention it. i got the circuit to work on a breadboard with a freeduino so i know that it works. and i do punctuate quite allot actually.

im just worried that the power going into the arduino through the digital pin from the sensor is damaging the arduino,

Yes it is.

so if you know the value of resistor that would be best for turning 9v into 5v so that it is the same as the output on a normal arduino board?

There is no such thing as a single resistor being able to do this.
We NEED to know what sort of tilt switch it is in order to tell you how to wire it up because there are lots of different types.

If the 328 itself is getting hot, that's usually a sign an output pin has been blowm, and its just a matter of time until the rest of the chip fails.

"there is a tilt sensor attached directly to the 9v pin, the power shouldn't damage the sensor, im just worried that the power going into the arduino through the digital pin from the sensor is damaging the arduino,"

If the 9V was going thru the tilt sensor to an input pin, that could damage it. A voltage divider could be used there to change the voltage swing seen from 0-9v down to 0-5V.
Do you have a link to the tilt sensor? And even better, a schematic of your setup?

And you should download a copy of the Promini schematic, shows the 5V pin (called VCC) that is an output from the Regulator.
This could be 3.3V or 5V, so it is labelled Vcc to be either.

http://www.oomlout.co.uk/tilt-switch-p-243.html
this is the tilt switch, it is very simple and basic and cheap, thanks for explaining about the vcc pin, i thought that that was only input, that might make it work

sholtob:
http://www.oomlout.co.uk/tilt-switch-p-243.html
this is the tilt switch, it is very simple and basic and cheap, thanks for explaining about the vcc pin, i thought that that was only input, that might make it work

That is a simple switch contact type sensor. Easiest way to interface it to your pro-mini is to wire one terminal of the sensor to arduino ground pin, the other terminal to your desired input pin. Then enable the internal pull-up resistor for that input pin. Results will be if digitalRead returns a 0 then sensors is 'tilted', if it returns a 1 then it's not 'tilted'. That way you need no external voltage or resistor for the sensor.

Lefty

thanks very much, it works now, i had just about got it to work with my origianal method but it was very prone to getting set of by accident, i tried what you said and its working much better :slight_smile: